This invention relates to an improved piston pin assembly. More particularly, the invention relates to a hollow piston pin assembly which has improved strength and durability.
Piston driven engines often employ piston pins to aid in providing communication between the pistonhead within the engine cylinder and the piston rod which acts in response to the motion of the pistonhead to supply power to the crank shaft.
Frequently, piston pins are hollow in configuration in order, for example, to reduce the weight of the reciprocating piston components. Because a hollow piston pin has a reduced strength, the forces on the pin during use result in increasing pin deflection and produce higher internal stresses. Increased pin deflection in turn causes increased bearing wear. If the deflection is of a sufficient magnitude, the pin may be permanently deformed. Pins so deformed must be replaced.
Clearly, a hollow piston pin having a configuration to minimize deflection is desirable.
Therefore, one object of the present invention is to provide an improved piston pin assembly.
Another object of the present invention is to provide an improved hollow piston pin assembly with improved strength.
A still further object of the present invention is to provide an improved hollow piston pin assembly with a reduced tendency to deflect under load conditions. Other objects and advantages of the present invention will become apparent hereinafter.
An improved piston pin assembly has now been discovered. This assembly includes a hollow tubular means, preferably substantially circular in outside cross-sectional area, which acts as the body of the piston pin. That is, the outside surface of the hollow tubular means acts in cooperation with the bearings, pistonhead and rod to facilitate the operation of the piston. In short, the hollow tubular means described above is a hollow piston pin as that term is generally used. In the present assembly, support means are positioned within a hollow space formed by the tubular means so as to inhibit deflection of the tubular means when the assembly is under load conditions, e.g. during engine operation. Thus, the present support means provides for improved piston pin strength without unduly affecting the weight reduction benefit of hollow piston pins.
In one embodiment, the support means of the present apparatus comprises at least, and preferably only, two separate plugs positioned a distance apart within the hollow space of the tubular means. These plugs are preferably positioned to support the point or points of the hollow tubular means which is subjected to maximum stress under load conditions. The outside cross-sectional area, preferably substantially circular configuration, of these plugs is substantially equal to the inside cross-sectional area, also substantially circular in configuration, of at least a portion of the hollow space of the tubular means so that each of the plugs is positioned or fits snugly into the hollow space.
The plugs are substantially cylindrical in shape and, in addition, more preferably are substantially solid, i.e. are not hollow. Solid plugs have been found to be effective to support the piston pin against deflection without unduly increasing weight included in the assembly.
In a further embodiment, the hollow space defined by the tubular means has a nonuniform cross-sectional area. Preferably the cross-sectional area of this hollow space varies in such a manner that the hollow space is substantially symmetrical with respect to shape and volume around the central axis of the tubular means. In one preferred system, two substantially identical, e.g. with respect to weight and geometry, plugs are positioned within the hollow space at points of substantially equal hollow space cross-sectional area, which area is neither the largest nor the smallest (i.e. at an intermediate cross-sectional area) within the hollow space. In a more preferred embodiment, the two plugs are positioned within the hollow space so as to be separated by a portion of the hollow space which has a smaller cross-sectional area relative to the cross-sectional area of the plugs. This feature provides additional strength to the assembly and facilitates more securely locating the plugs in the hollow space.
In general, and except as otherwise provided for herein, the assembly of the present invention may be fabricated from any suitable material or combination of materials of construction. The material of construction used for each component of the present apparatus may be dependent upon the particular application involved. Of course, the apparatus should be made of materials which are substantially unaffected, except for normal wear and tear, by the conditions at which the assembly is normally operated. Preferably, the present tubular means and supports are made of the same material of construction in order to provide maximum compatibility during manufacture and use.
These and other aspects and advantages of the present invention are set forth in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.